iio: amplifiers: hmc425a: add support for LTC6373 Instrumentation Amplifier
This adds support for LTC6373 36 V Fully-Differential Programmable-Gain Instrumentation Amplifier with 25 pA Input Bias Current. The user can program the gain to one of seven available settings through a 3-bit parallel interface (A2 to A0). Signed-off-by: Dumitru Ceclan <mitrutzceclan@gmail.com> Reviewed-by: Nuno Sa <nuno.sa@analog.com> Link: https://lore.kernel.org/r/20240220153553.2432-6-mitrutzceclan@gmail.com Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Dumitru Ceclan
Jonathan Cameron
parent
09ac57ac01
commit
a0e7a2b703
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@ -2,9 +2,10 @@
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/*
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* HMC425A and similar Gain Amplifiers
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*
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* Copyright 2020 Analog Devices Inc.
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* Copyright 2020, 2024 Analog Devices Inc.
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*/
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#include <linux/bits.h>
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#include <linux/bitops.h>
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#include <linux/device.h>
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#include <linux/err.h>
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@ -12,6 +13,7 @@
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#include <linux/iio/iio.h>
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#include <linux/iio/sysfs.h>
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#include <linux/kernel.h>
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#include <linux/math.h>
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#include <linux/mod_devicetable.h>
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#include <linux/module.h>
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#include <linux/platform_device.h>
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@ -20,10 +22,24 @@
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#include <linux/regulator/consumer.h>
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#include <linux/sysfs.h>
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/*
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* The LTC6373 amplifier supports configuring gain using GPIO's with the following
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* values (OUTPUT_V / INPUT_V): 0(shutdown), 0.25, 0.5, 1, 2, 4, 8, 16
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*
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* Except for the shutdown value, all can be converted to dB using 20 * log10(x)
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* From here, it is observed that all values are multiples of the '2' gain setting,
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* with the correspondent of 6.020dB.
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*/
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#define LTC6373_CONVERSION_CONSTANT 6020
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#define LTC6373_MIN_GAIN_CODE 0x6
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#define LTC6373_CONVERSION_MASK GENMASK(2, 0)
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#define LTC6373_SHUTDOWN GENMASK(2, 0)
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enum hmc425a_type {
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ID_HMC425A,
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ID_HMC540S,
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ID_ADRF5740
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ID_ADRF5740,
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ID_LTC6373,
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};
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struct hmc425a_chip_info {
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@ -34,6 +50,8 @@ struct hmc425a_chip_info {
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int gain_min;
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int gain_max;
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int default_gain;
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int powerdown_val;
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bool has_powerdown;
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int (*gain_dB_to_code)(int gain, int *code);
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int (*code_to_gain_dB)(int code, int *val, int *val2);
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@ -44,6 +62,7 @@ struct hmc425a_state {
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const struct hmc425a_chip_info *chip_info;
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struct gpio_descs *gpios;
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u32 gain;
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bool powerdown;
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};
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static int gain_dB_to_code(struct hmc425a_state *st, int val, int val2, int *code)
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@ -58,6 +77,8 @@ static int gain_dB_to_code(struct hmc425a_state *st, int val, int val2, int *cod
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if (gain > inf->gain_max || gain < inf->gain_min)
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return -EINVAL;
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if (st->powerdown)
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return -EPERM;
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return st->chip_info->gain_dB_to_code(gain, code);
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}
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@ -83,8 +104,17 @@ static int adrf5740_gain_dB_to_code(int gain, int *code)
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return 0;
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}
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static int ltc6373_gain_dB_to_code(int gain, int *code)
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{
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*code = ~(DIV_ROUND_CLOSEST(gain, LTC6373_CONVERSION_CONSTANT) + 3)
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& LTC6373_CONVERSION_MASK;
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return 0;
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}
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static int code_to_gain_dB(struct hmc425a_state *st, int *val, int *val2)
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{
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if (st->powerdown)
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return -EPERM;
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return st->chip_info->code_to_gain_dB(st->gain, val, val2);
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}
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@ -114,6 +144,16 @@ static int adrf5740_code_to_gain_dB(int code, int *val, int *val2)
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return 0;
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}
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static int ltc6373_code_to_gain_dB(int code, int *val, int *val2)
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{
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int gain = ((~code & LTC6373_CONVERSION_MASK) - 3) *
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LTC6373_CONVERSION_CONSTANT;
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*val = gain / 1000;
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*val2 = (gain % 1000) * 1000;
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return 0;
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}
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static int hmc425a_write(struct iio_dev *indio_dev, u32 value)
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{
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struct hmc425a_state *st = iio_priv(indio_dev);
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@ -192,6 +232,48 @@ static const struct iio_info hmc425a_info = {
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.write_raw_get_fmt = &hmc425a_write_raw_get_fmt,
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};
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static ssize_t ltc6373_read_powerdown(struct iio_dev *indio_dev,
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uintptr_t private,
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const struct iio_chan_spec *chan,
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char *buf)
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{
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struct hmc425a_state *st = iio_priv(indio_dev);
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return sysfs_emit(buf, "%d\n", st->powerdown);
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}
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static ssize_t ltc6373_write_powerdown(struct iio_dev *indio_dev,
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uintptr_t private,
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const struct iio_chan_spec *chan,
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const char *buf,
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size_t len)
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{
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struct hmc425a_state *st = iio_priv(indio_dev);
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bool powerdown;
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int code, ret;
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ret = kstrtobool(buf, &powerdown);
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if (ret)
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return ret;
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mutex_lock(&st->lock);
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st->powerdown = powerdown;
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code = (powerdown) ? LTC6373_SHUTDOWN : st->gain;
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hmc425a_write(indio_dev, code);
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mutex_unlock(&st->lock);
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return len;
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}
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static const struct iio_chan_spec_ext_info ltc6373_ext_info[] = {
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{
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.name = "powerdown",
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.read = ltc6373_read_powerdown,
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.write = ltc6373_write_powerdown,
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.shared = IIO_SEPARATE,
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},
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{}
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};
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#define HMC425A_CHAN(_channel) \
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{ \
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.type = IIO_VOLTAGE, \
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@ -201,10 +283,24 @@ static const struct iio_info hmc425a_info = {
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.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN), \
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}
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#define LTC6373_CHAN(_channel) \
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{ \
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.type = IIO_VOLTAGE, \
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.output = 1, \
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.indexed = 1, \
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.channel = _channel, \
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.info_mask_separate = BIT(IIO_CHAN_INFO_HARDWAREGAIN), \
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.ext_info = ltc6373_ext_info, \
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}
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static const struct iio_chan_spec hmc425a_channels[] = {
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HMC425A_CHAN(0),
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};
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static const struct iio_chan_spec ltc6373_channels[] = {
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LTC6373_CHAN(0),
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};
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static const struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
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[ID_HMC425A] = {
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.name = "hmc425a",
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@ -239,6 +335,19 @@ static const struct hmc425a_chip_info hmc425a_chip_info_tbl[] = {
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.gain_dB_to_code = adrf5740_gain_dB_to_code,
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.code_to_gain_dB = adrf5740_code_to_gain_dB,
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},
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[ID_LTC6373] = {
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.name = "ltc6373",
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.channels = ltc6373_channels,
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.num_channels = ARRAY_SIZE(ltc6373_channels),
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.num_gpios = 3,
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.gain_min = -12041, /* gain setting x0.25*/
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.gain_max = 24082, /* gain setting x16 */
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.default_gain = LTC6373_MIN_GAIN_CODE,
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.powerdown_val = LTC6373_SHUTDOWN,
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.has_powerdown = true,
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.gain_dB_to_code = ltc6373_gain_dB_to_code,
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.code_to_gain_dB = ltc6373_code_to_gain_dB,
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},
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};
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static int hmc425a_probe(struct platform_device *pdev)
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@ -279,8 +388,13 @@ static int hmc425a_probe(struct platform_device *pdev)
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indio_dev->info = &hmc425a_info;
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indio_dev->modes = INDIO_DIRECT_MODE;
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/* Set default gain */
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hmc425a_write(indio_dev, st->gain);
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if (st->chip_info->has_powerdown) {
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st->powerdown = true;
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hmc425a_write(indio_dev, st->chip_info->powerdown_val);
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} else {
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/* Set default gain */
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hmc425a_write(indio_dev, st->gain);
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}
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return devm_iio_device_register(&pdev->dev, indio_dev);
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}
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@ -293,6 +407,8 @@ static const struct of_device_id hmc425a_of_match[] = {
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.data = &hmc425a_chip_info_tbl[ID_HMC540S]},
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{ .compatible = "adi,adrf5740",
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.data = &hmc425a_chip_info_tbl[ID_ADRF5740]},
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{ .compatible = "adi,ltc6373",
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.data = &hmc425a_chip_info_tbl[ID_LTC6373]},
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{}
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};
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MODULE_DEVICE_TABLE(of, hmc425a_of_match);
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